JPH0616829A - Composite material of carbon fiber - Google Patents

Abstract

PURPOSE:To obtain a composite material of carbon fiber improved in processability during the production thereof, heat resistance, high-temp. mechanical property, and storage stability by incorporating a composition containing a polycarbodiimide compound and a cyanic ester compound. CONSTITUTION:The composite material contains a combination of a polycarbodiimide compound having 2 or more carbodiimide bonds per molecule [e.g. one represented by formula I (wherein X is H, a 1-9C alkyl, a 1-9C alkoxy, or a halogen)] and a cyanic ester compound having at least 2 cyanate groups per molecule [e.g. one represented by formula II (wherein X is a direct bond, -S-, -SO2-, -CH2-, etc.; and R1, R'1, R2, and R'2 each is H, a 1-9C alkyl, or a halogen)] as a matrix resin. This material is excellent in storage stability and in processability during the production thereof. The matrix enables the composite material to exhibit excellent heat resistance and mechanical properties in any storage environment.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel thermosetting resin-containing carbon fiber composite material.

[0002]

2. Description of the Related Art In recent years, carbon fiber composite materials have excellent strength,
Due to its high elastic modulus and light weight, it is widely used in various structural members such as aircraft structural materials, skis, tennis and golf clubs.

An epoxy resin is known as a matrix resin for carbon fibers which has been most commonly used conventionally. However, due to the expansion of the application of structural composite materials to aircraft and the like, there is a high demand for heat resistance, and attempts have been made to apply polyimide resins, cyanate ester resins, etc. instead of epoxy resins.

Although the cured product of the polyimide resin is extremely excellent in heat resistance, it is inconvenient for impregnation into carbon fiber due to its poor solubility in an organic solvent. There are many problems with the tee. On the other hand, sialic acid ester resin is disclosed in Japanese Patent Publication No. 46-411.
It has good heat resistance as disclosed in No. 12, and although the processability, which is a drawback of the polyimide resin, has also been improved, it has high hygroscopicity, heat resistance after moisture absorption, for example, heat distortion temperature. It has the drawback of going down.

For the purpose of solving such a problem, a method of using the above-mentioned polyimide resin and cyanate ester resin in combination is disclosed in Japanese Patent Laid-Open No. 50-129700 and an attempt to put it into practical use is made. We have not fully solved the problems we have done. Further, the polycarbodiimide resin disclosed in JP-A-63-161027 requires curing conditions at a high temperature of 300 ° C. or higher in order to improve heat resistance, and as the material is cured at a high temperature, There is a problem that mechanical properties (bending strength, etc.) are reduced.

According to Japanese Patent Laid-Open No. 2-218751, by using an aromatic cyanate ester compound and an aromatic polycarbodiimide compound in combination, good heat resistance is exhibited even in a hygroscopic environment. When the composition is used for a laminated board, there are drawbacks such as poor storage stability of a resin solution before making a prepreg such as glass cloth, and it is not yet in a satisfactory state.

[0007]

DISCLOSURE OF THE INVENTION The present invention is capable of exhibiting the above-mentioned storage stability, the processability during the production of carbon fiber composite materials, and the excellent heat resistance and mechanical properties in any storage environment. It is to provide a carbon fiber composite material using a novel matrix resin.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the composition of a compound having a carbodiimide bond and a compound having a cyanate ester group is The inventors have found that they are fit for purpose and arrived at the present invention.

That is, the present invention provides (1) a composition containing (A) a polycarbodiimide compound having two or more carbodiimide bonds in the molecule, and (B) at least two or more cyanate ester compounds in the molecule. Containing carbon as a matrix resin (2) The polycarbodiimide compound has the following formula (1)
A group having 5 to 95 equivalent parts of a group having a structural unit represented by Chemical formula 4 and 95 to 5 equivalent parts of a group having a structural unit represented by the following formula (2) (Chemical formula 4) are contained. A carbon fiber composite material according to item (1) above, which is a carbodiimide copolymer sealed with a group group and having a weight average molecular weight of 10,000 or less.

[0010]

[Chemical 4] (3) The aromatic group at the molecular end of the polycarbodiimide compound is a phenyl group, an ortho-tolyl group, a meta-tolyl group, a para-tolyl group, a dimethylphenyl group, a chlorophenyl group, a trifluoromethylphenyl group, a naphthyl group,
Carbon fiber composite material according to item (2) above, which is at least one selected from the group consisting of isopropylphenyl group and diisopropylphenyl group. (4) Weight of the polycarbodiimide compound represented by the following formula (3): The carbon fiber composite material as described in the above item (1), which has an average molecular weight of 20,000 or less.

[0011]

[Chemical 5] (In the formula, X is a hydrogen atom, lower alkyl having 1 to 9 carbon atoms,
Representing a lower alkoxy having 1 to 9 carbon atoms or a halogen atom) (5) The carbon fiber composite according to item (1), wherein the cyanate ester compound is represented by the following formula (4). Material

[0012]

[Chemical 6] R ₁ , R ′ ₁ , R ₂ and R ′ ₂ each represent a hydrogen atom, a lower alkyl having 1 to 9 carbon atoms or a halogen atom)
Is. A detailed description of the configuration will be given below.

The organic compound containing two or more carbodiimide bonds in the molecule used in the present invention has the formula (5) in the molecular chain.
Any of those having the structure of can be used, but it is particularly preferable to use polycarbodiimide. -N = C = N- (5) Polycarbodiimide is a polymer compound having a large number of carbodiimide bonds in its molecular chain, and this compound itself is known, and accelerates carbodiimidization of isocyanate from organic polyisocyanate. It can be produced in the presence of a catalyst.

Examples of organic polyisocyanates used are phenylene-1,3-diisocyanate, phenylene-1,4-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, 1-methoxybenzene- 2,4-diisocyanate, 1-chlorophenylene diisocyanate, tetrachlorophenylene diisocyanate, metaxylylene diisocyanate,
Paraxylylene diisocyanate, diphenylmethane-
4,4'-diisocyanate, diphenyl sulfide-4,4 '
-Diisocyanate, diphenylsulfone-4,4'-diisocyanate, diphenylether-4,4'-diisocyanate, diphenylether-3,4'-diisocyanate, diphenylketone-4,4'-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene − 1,4−
Diisocyanate, naphthalene-1,5-diisocyanate, 2,4'-biphenyldiisocyanate, 4,4'-biphenyldiisocyanate, 3,3'-methoxy-4,4'-biphenyldiisocyanate, anthraquinone-2,6-diisocyanate, tri Phenylmethane-4,4'-diisocyanate, azobenzene-4,4'-diisocyanate and dimers or higher polynuclears of these organic polyisocyanates and organic polyisocyanates are stoichiometric with respect to polyfunctional active hydrogen compounds. Examples thereof include a terminal isocyanate prepolymer and the like, which are obtained by using an excess amount thereof.

In the present invention, it is preferable to use a polycarbodiimide whose molecular weight is regulated because the heat fluidity becomes better. This polycarbodiimide whose molecular weight is regulated can be produced from the above organic polyisocyanate and an organic monoisocyanate as a molecular weight modifier in the presence of a catalyst that promotes carbodiimidization of isocyanate. As the organic monoisocyanate used as a molecular weight regulator, phenyl isocyanate,
(Ortho, meta, para) -tolyl isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate, methyl isocyanate, butyl isocyanate, chlorophenyl isocyanate, trifluoromethylphenyl isocyanate, naphthyl isocyanate,
And the like, for example, organic polyisocyanate 10
5 to 50 parts by mole can be used with respect to 0 parts by mole.

Various catalysts can be used as the catalyst for promoting the carbodiimidization of isocyanate, but 1-phenyl-2-phosphoren-1-oxide and 3-methyl-1-phenyl-2-phosphoren-1- Oxide, 1-phenyl-2-phosphorene-1-sulfide, 1-ethyl-2-phosphorene-1-oxide, 1-ethyl-3-methyl-2-phospholen-1-oxide and their corresponding isomers, 3-phosphorenes are good. The amount of catalyst is 0.01 with respect to the total amount of isocyanate.
It can be used between -1%.

In the present invention, the aromatic cyanate ester compound having two or more cyanate ester groups in the molecule is a compound having a cyanate group represented by the general formula (6). (In the formula, R ₁ is an aromatic polyvalent organic group, the cyanate ester group is an organic group, the cyanate ester group is directly bonded to the aromatic ring of the organic group R ₁ , and n is The polycyanate compound is generally an integer of 2 or more, usually 10 or less.) The polycyanate compound is generally a known method in which a corresponding polyhydric phenol compound is reacted with a cyanogen halide (for example, JP-B-41-1928). ). Specific examples of polyfunctional cyanate esters are 1,3- or 1,4-dicyanate benzene, 1,3-
3,5-tricyanate benzene, 1,3-, 1,4-, 1,6
-, 1,8-, 2,6- or 2,7-dicyanatonaphthalene, 1,3,6-tricyanatonaphthalene, 2,2'- or 4,4'-dicyanate biphenyl, bis (4-Cyanatophenyl) methane, 2,2-bis (4-cyanatophenyl) propane, 2,2-bis (3,5-dichloro-4-)
Cyanatophenyl) propane, bis (4-cyanatophenyl) ether, bis (4-cyanatophenyl)
Thioether, bis (4-cyanatophenyl) sulfone, tris (4-cyanatophenyl) phosphite,
Tris (4-cyanatophenyl) phosphate, and a benzene polynuclear polycyanate compound obtained by the reaction of a phenol resin and a cyanogen halide (for example,
The teachings in JP-B-45-11712 and 55-9433 can be mentioned. A divalent cyanate ester derived from a dihydric phenol such as 2,2-bis (4-hydroxyphenyl) propane, from the standpoints of being readily available and imparting good properties to the moldability and final resin. The compounds are particularly preferably used. Further, a polycyanate compound obtained by reacting an initial condensate of phenol and formaldehyde with cyanogen halide is also useful.

In the composition of the present invention, the above polycyanate ester compound may be used alone, or the oligomer (prepolymer) derived from this polycyanate ester compound may be used alone, or these may be mixed and used. May be. The prepolymer can be obtained by polymerizing a polycyanate compound in the presence of a catalyst such as mineral acid, Lewis acid, sodium carbonate, salts such as lithium chloride, or phosphoric acid esters. These prepolymers have an s-triazine ring formed by trimerization of the cyanate group in the cyanate ester in the molecule, and preferably have an average molecular weight of about 400 to 6000 (hereinafter Abbreviated as cyanate ester compound).

When reacting the polycarbodiimide compound and the cyanate ester compound, for example, triethylenediamine, N, N-dimethylbenzylamine, N-
Tertiary amines such as methylmorpholine, 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4
-Imidazoles such as methylimidazole, metal octylates, metal naphthenates, acetylacetone metal salts,
Stearic acid metal salt, butyl titanate, metal salts such as propylaluminum, tin tetrachloride, iron chloride, preferably one or more catalysts capable of promoting crosslinking reticulation, such as chlorides such as aluminum chloride, 0.01% by weight
It has been found that the addition of 5 to 5% by weight can enhance the curing reaction rate of both compounds. The blending ratio of the polycarbodiimide compound and the cyanate ester compound of the present invention is useful in a wide range of weight ratios of 95: 5 to 10:90, but particularly in the range of 90:10 to 30:70. preferable.

The method for producing a carbon fiber composite material using the composition of the present invention as a matrix resin can be carried out by the following two methods, a melt impregnation method and a solution impregnation method. First, regarding the melt impregnation method, a powdery polycarbodiimide having a controlled molecular weight and a cyanate ester compound are sufficiently mixed to prepare a composition. Next, the powdery composition is melted at 100 to 150 ° C., and carbon fiber or
A cloth made of carbon fiber is impregnated to prepare a prepreg. Laminating the prepregs thus obtained,
The laminated prepreg is heated and pressed to cure the resin component, whereby a composite material having excellent heat resistance and mechanical properties can be obtained.

On the other hand, in the solution impregnation method, a solution is prepared by dissolving the above powdery composition in an organic solvent capable of dissolving, or a cyanate ester compound is dissolved in a solution-like polycarbodiimide having a controlled molecular weight, A composition varnish is prepared. Next, the composition varnish is impregnated into carbon fiber or a cloth made of carbon fiber, and the solvent is dried and removed at an appropriate temperature to prepare a prepreg. A desired composite material can be obtained by laminating the prepregs and heat-pressing.

The heating temperature at this time is usually 150 ° C. to 30 ° C.
The temperature is about 0 ° C. and the pressure condition is usually about 5 to 100 kg / cm ² , and if necessary, post-curing may be further performed at about 200 to 300 ° C. after decompressing. When the composition of the present invention described above is put to practical use, auxiliary agents such as a curing accelerator, an adhesion promoter, an antifoaming agent, a flame retardant, and a release agent, an inorganic filler, a colorant, and the like are mixed and used. It doesn't matter.

[0023]

EXAMPLES Examples will be shown below to specifically describe the embodiments of the present invention. Example 1 Controlled molecular weight polycarbodiimide synthesized by heating diphenylmethane-4,4'-diisocyanate and phenylisocyanate in xylene in the presence of 3-methyl-1-phenyl-2-phosphorene-1-oxide catalyst. (Hereinafter abbreviated as PCI, average molecular weight of about 40
00) to 80 parts by weight, 20 parts by weight of 2,2-bis (4-cyanatophenyl) propane (hereinafter abbreviated as BCPP, manufactured by Rhone-Poulin: trade name AroCy B-10) is added and mixed sufficiently. A powdery resin composition was obtained. This powdery resin composition was melted at 110 to 150 ° C., impregnated with carbon fibers and wound on a drum. The impregnated carbon fiber was sandwiched by two rollers, and the gap between them was controlled to adjust the resin content to 45% by weight to obtain a prepreg. 8 sheets of the obtained prepregs were laminated in one direction, and at 30 ° C at 30 ° C.
Thermoforming was carried out at a pressure of 40 kg / Cm ² per minute to obtain a laminated plate having a thickness of about 1.6 mm. Room temperature (25 ℃) and hot (200
The physical properties at (° C.) and the storage stability of the powdery composition were as follows. Bending strength (25 ℃) 60 Kgf / mm ² (200 ℃) 50 Kgf / mm ² Flexural modulus (25 ℃) 5500 Kgf / mm ² (200 ℃) 3800 Kgf / mm ² Storage stability of powdery resin composition (25 ℃) No change for more than 3 months

Example 2 A prepreg was prepared in the same manner as in Example 1, and the obtained prepreg was laminated in one direction and pressed at 300 ° C. for 30 minutes to obtain a molded product. Room temperature (25 ℃) and hot (200
The physical properties at (° C.) were as follows.

Example 3 A molded article was obtained in the same manner as in Example 1 except that 50 parts by weight of BCPP was added to 50 parts by weight of PCI. The physical properties of this molded product at room temperature (25 ° C.) and hot (200 ° C.), and the storage stability of the powdery composition were as follows. Bending strength (25 ℃) 65 Kgf / mm ² (200 ℃) 54 Kgf / mm ² Flexural modulus (25 ℃) 5800 Kgf / mm ² (200 ℃) 4000 Kgf / mm ² Storage stability of powdered resin composition (25 ℃) No change for more than 3 months

Example 4 A powdery composition was prepared in the same manner as in Example 1 and
It was melted at 10 ° C to 150 ° C and impregnated with a cloth made of carbon fiber to prepare a prepreg. The prepregs were laminated and thermocompression molded at 250 ° C. for 30 minutes to obtain a laminated plate.
The physical properties of this molded product at room temperature (25 ° C) and hot (200 ° C) were as follows.

Comparative Example 1 A molded product was obtained in the same manner as in Example 1 except that BCPP was not used. Room temperature (25 ℃) and hot (200
The physical properties at (° C.) were as follows.

Example 5 The powdery resin composition obtained in Example 1 was treated with N-methyl-
It was dissolved in a 2-pyrrolidone solvent to prepare a composition varnish having a concentration of 30 wt%. Next, a cloth made of carbon fiber was dipped in the composition varnish, the excess resin solution was removed by a squeezing roll, and the solution was passed through a hot air drying oven at 130 ° C. to volatilize and remove the organic solvent to obtain a prepreg. The resin content of the prepreg was measured by a thermal decomposition method and as a result, it was about 40%.

Eight sheets of the obtained prepreg were laminated to form 250
Thermocompression molding at a pressure of 40 Kg / Cm ² for 30 minutes at ℃, thickness approximately
A 1.6 mm laminated plate was obtained. The physical properties of this molded product at room temperature (25 ° C.) and hot (200 ° C.), and the storage stability of the composition varnish were as follows. Bending strength (25 ℃) 62 Kgf / mm ² (200 ℃) 53 Kgf / mm ² Flexural modulus (25 ℃) 5600 Kgf / mm ² (200 ℃) 3900 Kgf / mm ² Composition varnish Storage stability (25 ℃ ) No change for more than 1 month

Example 6 Mixture of 80 parts by mole of 2,4-TDI and 20 parts by mole of 2,6-TDI (trade name: TDI 80, manufactured by Mitsui Toatsu Chemicals, Inc.) 92
g, 9 g of phenyl isocyanate are dissolved in toluene, and 3-methyl-1-phenyl-2-phosphorene-1-
0.36 g of an oxide catalyst was added and polymerization was carried out at 110 ° C. to obtain a polycarbodiimide resin varnish with a controlled molecular weight (average molecular weight: about 1000, solid content: 30 w
t%). To this varnish, 19 g of BCPP was added and uniformly dissolved to prepare a composition varnish (weight ratio 80/20).

Next, the cloth made of carbon fiber is dipped in the composition varnish and the excess resin solution is removed by a squeezing roll,
It was passed through a hot air drying oven at 0 ° C. to volatilize and remove the organic solvent to obtain a prepreg. The resin content of the prepreg was measured by a thermal decomposition method and was found to be about 45%. 8 sheets of the obtained prepregs are laminated, and 40 kg / Cm at 250 ° C for 30 minutes.
Thermoforming was performed at a pressure of ² to obtain a laminated plate having a thickness of about 1.6 mm.
The physical properties of this molded product at room temperature (25 ° C.) and hot (200 ° C.), and the storage stability of the composition varnish were as follows. Bending strength (25 ℃) 80 Kgf / mm ² (200 ℃) 66 Kgf / mm ² Flexural modulus (25 ℃) 6000 Kgf / mm ² (200 ℃) 4100 Kgf / mm ² Storage stability of composition varnish (25 ℃) No change for more than 1 month

Comparative Example 2 A molded product was obtained in the same manner as in Example 6 except that BCPP was not used. Room temperature (25 ℃) and hot (200
The physical properties at (° C.) were as follows.

Comparative Example 3 30 g of 2,4-TDI and 0.3 g of 3-methyl-1-phenyl-2-phosphorene-1-oxide catalyst were mixed with 35 m of toluene.
1 and 25 ml of methyl ethyl ketone were added to a mixed solvent,
Reaction was carried out at 60 ° C. for 3 hours to obtain a suspension-like polycarbodiimide resin varnish. To this varnish, 5.6 g of BCPP was added and uniformly dissolved to prepare a composition varnish (weight ratio 80/2.
0). A molded product was obtained in the same manner as in Example 6 using this composition varnish. Room temperature (25 ℃) and hot (200
The physical properties at (° C.) and the storage stability of the composition varnish were as follows. Bending strength (25 ℃) 82 Kgf / mm ² (200 ℃) 67 Kgf / mm ² Flexural modulus (25 ℃) 6100 Kgf / mm ² (200 ℃) 4050 Kgf / mm ² Storage stability of composition varnish (25 ℃) 1 day after preparation, gelation

[0034]

As described above, the carbon fiber composite material of the present invention is obtained by using a composition containing a polycarbodiimide compound and a cyanate ester compound as a matrix resin.
The processability, heat resistance, mechanical properties at high temperature, and storage stability of the composition during the production of carbon fiber composite materials have been greatly improved, and their industrial utility value is extremely high.

Claims (5)

[Claims] 1. A polycarbodiimide compound having (A) two or more carbodiimide bonds in the molecule, and (B)
A carbon fiber composite material comprising a composition containing at least two cyanate ester compounds in its molecule as a matrix resin. 2. A polycarbodiimide compound having groups 5 to 9 having a structural unit represented by the following formula (1) (formula 1).
5 equivalent parts and 95 to 5 equivalent parts of a group having a structural unit represented by the following formula (2) (Chemical Formula 1) are contained, the terminal of the polymer molecule is sealed with an aromatic group, and the weight average molecular weight is 10,000 or less. 2. The carbon fiber composite material according to claim 1, which is a carbodiimide copolymer. [Chemical 1] 3. The aromatic group at the molecular end of the polycarbodiimide compound is a phenyl group, ortho-tolyl group, meta-tolyl group, para-tolyl group, dimethylphenyl group, chlorophenyl group, trifluoromethylphenyl group, naphthyl group. The carbon fiber composite material according to claim 2, wherein the carbon fiber composite material is at least one selected from the group consisting of isopropyl phenyl group and diisopropyl phenyl group. 4. The carbon fiber composite material according to claim 1, wherein the polycarbodiimide compound has a weight average molecular weight represented by the following formula (3) (Formula 2) of 20,000 or less. [Chemical 2] (In the formula, X is a hydrogen atom, lower alkyl having 1 to 9 carbon atoms,
Represents a lower alkoxy having 1 to 9 carbon atoms or a halogen atom) 5. The carbon fiber composite material according to claim 1, wherein the cyanate ester compound is represented by the following formula (4) (formula 3). [Chemical 3] R ₁ , R ′ ₁ , R ₂ and R ′ ₂ each represent a hydrogen atom, a lower alkyl having 1 to 9 carbon atoms or a halogen atom)